1. Field of the Invention
The present invention relates to optically active bisoxazoline compounds, a process for producing them and a process for producing optically active cyclopropanecarboxylic acid derivatives using them.
2. Description of Related Arts
The optically active cyclopropanecarboxylic acid esters are important compounds as intermediates for pharmaceuticals and pesticides. For example, (+)-2,2-dimethyl-3-(2-methyl-1-propenyl)cyclopropanecarboxylic acid, also known as chrysanthemum-monocarboxylic acid, constitutes the acid component of synthetic pyrethroid insecticides.
Conventionally, as the methods for directly producing optically active cyclopropanecarboxylic acid esters by synthetic technique, for example, a method has been known in which a prochiral olefin is reacted with a diazoacetic acid ester in the presence of an asymmetric copper complex using an optically active bis [2-(4,5-diphenyl-1,3-oxazolinyl)]methane as the ligand (Tetrahedron Lett., 32, 7373 (1991)).
Since, however, this method has problems that the raw material used for synthesizing the ligand is expensive and that the method for synthesizing the ligand is complicated, this method can not always be said to be an industrially advantageous method.
The present inventors have completed the present invention as the result of an extensive study conducted for the purpose of providing optically active bisoxazoline compounds useful as asymmetric ligands for copper complexes which are used in preparing optically active cyclopropanecarboxylic acid esters by reacting an olefin with a diazoacetic acid ester.